Defines a family of algorithms, encapsulates each one, and makes them interchangeable.
Category:
Behavioral
UML Diagram:
Description of the Demonstration:
A class called Duck is created along with two "families" of algorithms:
QuackBehavior and FlyBehavior. The QuackBehavior parent class has three
subclasses: Quack, Squeak, and MuteDuck. The FlyBehavior parent class
has two subclasses: FlyWithWings, and FlyNoWay. When an instance of one
of the subclasses of Duck (see UML diagram) is created it is given an
appropriate instance of one subclass of QuackBehavior and one subclass
of FlyBehavior. Because all subclasses implement the common interfaces
an instance of a subclass of Duck can be composed with its appropriate
quack and fly behavior at run time. These behaviors can also be easily
changed while the application is running.
When the demonstration program is run an instance of each of the subclasses
of Duck is created then the quack() and fly() functions are called on
each of the "ducks". Note in the UML diagram that a swim() method has
also been implemented in Duck. This behavior could also be extracted
into a third family of algorithms and swimming handled the same way as
Quack and Fly.
Code:
Click here to download a
zip file containing all the source files and an executable of the
Demonstration. See the _ReadMe.txt file in the zip.
